Solid electrolytic capacitor with cathode terminal and anode terminal

ABSTRACT

A solid electrolytic capacitor including a capacitor element having an anode member and a cathode member, an anode terminal electrically connected with the anode member, a cathode terminal electrically connected with the cathode member, and a mold resin portion covering the capacitor element; wherein the cathode terminal has an upper step portion in face-to-face contact with the cathode member and a lower step portion exposed out of the mold resin portion and a bottom surface of the mold resin portion and an upper surface of the lower step portion of the cathode terminal are disposed in an approximately same plane.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a solid electrolytic capacitor in whichportions of an anode terminal and a cathode terminal connected with acapacitor element are exposed out of a mold resin portion withoutentering in the mold resin portion.

2. Description of the Related Art

As a conventional solid electrolytic capacitor, for example, a solidelectrolytic capacitor having a structure shown in FIG. 5 has beenknown. The solid electrolytic capacitor is provided with a capacitorelement 101 obtained by successively forming a dielectric layer, acathode layer, and a cathode lead-out layer on a circumferential surfaceof an anode body in which an anode lead 121 is implanted, a mold resinportion 106, an anode terminal 107, and a cathode terminal 108. Portionsof the anode terminal 107 and the cathode terminal 108 are exposed outof the mold resin portion 106 and the exposed portions are bent alongthe circumferential surface of the mold resin portion 106.

To produce such a solid electrolytic capacitor having theabove-mentioned structure, it is required to carry out a processaccording to which the capacitor element 101 is coated with the moldresin portion 106 and thereafter the anode terminal 107 and the cathodeterminal 108 exposed out of the mold resin portion 106 are bent alongthe circumferential surface of the mold resin portion 106. However, inthe bending process, it is practically difficult to perpendicularly bendthe anode terminal 107 and the cathode terminal 108 and thus, strain toa certain extent is generated. Due to this strain, the produced solidelectrolytic capacitor becomes larger than standardized sizes and itresults in a problem of defective products. Further, to bend the anodeterminal 107 and the cathode terminal 108, a margin for bending isrequired and therefore the size of the mold resin portion 106 has to belarge to a certain degree and accordingly, it is difficult to make thesolid electrolytic capacitor compact and low in height and improve thevolume efficiency of the capacitor element 101. Further, there is aproblem that a lead-out distance from the anode lead 121 to the exposedportion to be the terminal of the anode terminal 107 and a lead-outdistance from the cathode lead-out layer to the exposed portion to bethe terminal of the cathode terminal 108 become long and accordingly, anESR of a solid electrolytic capacitor is increased.

In order to solve the above-mentioned problems, solid electrolyticcapacitors having structures as described in a Prior Art 1 (JapaneseUnexamined Patent Publication No. 2001-244145) and a Prior Art 2(Japanese Unexamined Patent Publication No. 2001-167976) have beenproposed.

That is, in the Prior Art 1, there is proposed a solid electrolyticcapacitor in which a bottom surface of a mold resin portion and bothlower surfaces of an anode terminal and a cathode terminal exposed outof the mold resin portion are in a same plane. However, in productionprocess of a solid electrolytic capacitor with such a structure, it isrequired to protect lower surfaces of the anode terminal and the cathodeterminal with an insulating tape or the like in order to prevent themold resin from penetrating the respective lower surfaces of the anodeterminal and the cathode terminal at the time of molding after the anodeterminal and the cathode terminal are connected respectively to thecapacitor element. Further, since it is impossible to completely preventfrom the penetration of the mold resin even if the insulating tape orthe like is adhered to the lower surfaces of the anode terminal and thecathode terminal, there occurs a problem of defective products.Furthermore, it is required to form a space in an interface between anupper mold and a lower mold at the time of molding in consideration ofthe thickness of the insulating tape; however, the pressure of the moldsto the insulating tape is not so high and it also results in a problemthat the mold resin leaks to the adhered surface of the insulating tape.

On the other hand, in the Prior Art 2, the volume efficiency of acapacitor element is improved by decreasing the volume of a mold resinportion by insulating an anode terminal made of a first conductive sheetand a cathode terminal made of a second conductive sheet with aninsulating sheet. However, to produce a solid electrolytic capacitorwith such a structure, a process of adhering an insulating sheet to bothconductive sheets to be the anode terminal and the cathode terminal isrequired. Further, with such a structure, the contact surface areabetween the capacitor element and the cathode terminal is narrowed andat the same time, the lead-out distance between the cathode layer of thecapacitor element and the exposed portion of the cathode terminalbecomes not smaller than the thickness of the insulating sheet andaccordingly, there occurs a problem that the ESR of the solidelectrolytic capacitor cannot be decreased.

SUMMARY OF THE INVENTION

In view of above circumstances, an object of the present invention is todecrease defects of products and improve production efficiency.

According to one aspect of the invention, there is provided a solidelectrolytic capacitor comprising a capacitor element having an anodemember and a cathode member, an anode terminal electrically connectedwith the anode member, a cathode terminal electrically connected withthe cathode member, and a mold resin portion covering the capacitorelement; wherein

the cathode terminal has an upper step portion in face-to-face contactwith the cathode member and a lower step portion exposed out of the moldresin portion and

a bottom surface of the mold resin portion and an upper surface of thelower step portion of the cathode terminal are disposed in anapproximately same plane.

Other objects, features and advantages of the present invention willbecome more fully understood from the detailed description givenhereinbelow and the accompanying drawings which are given by way ofillustration only, and thus are not to be considered as limiting thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a solid electrolytic capacitoraccording to a first embodiment of the invention;

FIG. 2 is a cross-sectional view showing a solid electrolytic capacitoraccording to a second embodiment of the invention;

FIG. 3 is a schematic perspective view of the solid electrolyticcapacitor of FIG. 2 observed from the X-direction;

FIG. 4 is a cross-sectional view showing a capacitor element accordingto the first embodiment and the second embodiment of the invention; and

FIG. 5 is a cross-sectional view showing a conventional solidelectrolytic capacitor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(First Embodiment)

FIG. 1 is a cross-sectional view of a solid electrolytic capacitoraccording to the first embodiment of the invention. The electrolyticcapacitor comprises a capacitor element 1, a mold resin portion 6, ananode terminal 7, and a cathode terminal 8. At least respective lowersurfaces and respective side surfaces of exposed portions of an anodeterminal 7 and a cathode terminal 8 exposed out of a mold resin portion6 are plated. The capacitor element 1 of the present embodiment has astructure shown, for example, in FIG. 4. That is, a dielectric layer 3and a cathode member 4 including a cathode layer 41 and a cathodelead-out layer 42 are successively layered on a circumferential surfaceof an anode body 22 in which an anode lead 21 is implanted. As the anodelead 21, the anode body 22, the dielectric layer 3, the cathode layer 41and a cathode lead-out layer 42, any of various materials that are knownin the art forming solid electrolytic capacitors can be used. Each ofthe dielectric layer 3, the cathode layer 41 and a cathode lead-outlayer 42 may be made of a single layer or a plurality of layers.Further, in the capacitor element 1, it is not necessary to use theanode body 22 in which the anode lead 21 is implanted, a metallic foilsuch as an aluminum foil may be used as the anode body 22.

In the present specification, an explanation is given by referring theanode lead 21 as an anode member 2 of the capacitor element 1, and thecathode layer 41 and the cathode lead-out layer 42 as a cathode member 4of the capacitor element 1.

The anode member 2 and the cathode member 4 are connected with an anodeterminal 7 and a cathode terminal 8, respectively. The anode terminal 7has a rising portion 71 and the anode member 2 and the exposed portionof the anode terminal 7 are connected with each other via the risingportion 71. A shape of the anode terminal 7 is not particularly limitedto the shape shown in FIG. 1. For example, the anode terminal 7 having asufficient height for direct connection with the anode member 2 may beused or as shown in FIG. 2, the anode member 2 and the anode terminal 7may be connected via a conductive member 9.

The cathode terminal 8 has an upper step portion 81 and a lower stepportion 82 and a step part is formed between the upper step portion 81and the lower step portion 82. The upper step portion 81 of the cathodeterminal 8 is connected with the lower surface of the cathode member 4in the inside of the mold resin portion 6 in such a manner that an uppersurface of the upper step portion 81 of the cathode terminal 8 is inface-to-face contact with the lower surface of the cathode member 4. Onthe other hand, the lower step portion 82 of the cathode terminal 8 isexposed out of the mold resin portion 6. An upper surface of the lowerstep portion 82 of the cathode terminal 8 and a bottom surface of themold resin portion 6 are disposed in an approximately same plane and theupper surface of the lower step portion 82 is brought into contact withthe bottom surface of the mold resin portion 6. Namely, the uppersurface of the lower step portion 82 of the cathode terminal 8 and thebottom surface of the mold resin portion 6 are disposed to beapproximately flushed with each other.

The exposed portion of the anode terminal 7 and the lower step portion82 of the cathode terminal 8 are respectively extended in the directionin which the anode member 2 and the cathode member 4 of the capacitorelement 1 are aligned and exposed out of the mold resin portion 6. Thoselower surfaces and side surfaces exposed out of the mold resin portion 6are plated respectively. According to the above-mentioned configuration,at the time of mounting the solid electrolytic capacitor on a substrate,solder fillet can easily be observed.

(Second Embodiment)

FIG. 2 is a cross-sectional view of a solid electrolytic capacitoraccording to the second embodiment of the invention. The electrolyticcapacitor comprises a capacitor element 1, a mold resin portion 6, ananode terminal 7, and a cathode terminal 8. The capacitor element 1 hasthe same structure as the first embodiment of FIG. 4. An anode member 2is connected with the anode terminal 7 via a conductive member 9 and acathode member 4 is connected with a cathode terminal 8. Herein, theshape, material, or the like of the conductive member 9 is notparticularly limited and those which can connect the anode member 2 withthe anode terminal 7 by a process such as resistance welding and whichhave conductivity in certain degree may be used.

The cathode terminal 8 has an upper step portion 81 and a lower stepportion 82 and a step part is formed between the upper step portion 81and the lower step portion 82. The upper step portion 81 of the cathodeterminal 8 is connected with the lower surface of the cathode member 4in the inside of the mold resin portion 6 and the lower step portion 82of the cathode terminal 8 is exposed out of the mold resin portion 6. Anupper surface of the lower step portion 82, a bottom surface of the moldresin portion 6, and an upper surface of the anode terminal 7 aredisposed in an approximately same plane. Namely, the upper surface ofthe lower step portion 82, the bottom surface of the mold resin portion6, and the upper surface of the anode terminal 7 are disposed to beapproximately flushed with each other. The upper surface of the lowerstep portion 82 of the cathode terminal 8 and the upper surface of theexposed portion of the anode terminal 7 are respectively brought intocontact with the bottom surface of the mold resin portion 6. Further,the cathode terminal 8 has a rising portion (side portion) 83 upwardlyextending from both ends in the width direction of the upper stepportion 81 to a direction approximately perpendicular to the directionin which the anode member 2 and the cathode member 4 are aligned. FIG. 3is a schematic perspective view of the solid electrolytic capacitor ofFIG. 2 observed from the X-direction.

As shown in FIG. 3, the rising portion (side portion) 83 is connectedwith side surfaces of the cathode member 4 of the capacitor element 1.According to the configuration, the contact surface area between thecathode member 4 and the cathode terminal 8 can further be widened andaccordingly, the ESR of the solid electrolytic capacitor can further belowered. In order to further widen the contact surface area between thecathode member 4 and the cathode terminal 8, it is preferable to form anextended portion 83 a extending from the rising portion 83 as shown inFIG. 2. The extending direction of the extended portion 83 a is notparticularly limited; however, in a case where the rising portion 83rises from a point nearest to the anode terminal 7 of the upper stepportion 81, the extended portion 83 a is preferable to be extended inthe direction from the anode member 2 side toward the cathode member 4side. By forming such a extended portion 83, the contact surface areabetween the capacitor element 1 and the cathode terminal 8 can furtherbe widened and accordingly, the ESR of the solid electrolytic capacitorcan further be lowered.

Further, in the present embodiment, the anode terminal 7 and the lowerstep portion 82 of the cathode terminal 8 is respectively exposed out ofthe mold resin portion 6 and those are extended in the direction inwhich the anode member 2 and the cathode member 4 are aligned, same asthose of the first embodiment. Accordingly, at the time of mounting thesolid electrolytic capacitor on a substrate, solder fillet can easily beobserved and adhesion between the solid electrolytic capacitor and thesubstrate can be improved.

In the solid electrolytic capacitor of FIG. 2, the anode terminal 7 andthe lower step portion 82 of the cathode terminal 8 is respectivelyexposed out of the mold resin portion 6 and side surfaces of the exposedportions are plated. Accordingly, solder fillet can easily be observedat the time of mounting the solid electrolytic capacitor on thesubstrate.

As described above in detail, according to one aspect of the invention,there is provided a solid electrolytic capacitor comprising a capacitorelement having an anode member and a cathode member, an anode terminalelectrically connected with the anode member, a cathode terminalelectrically connected with the cathode member, and a mold resin portioncovering the capacitor element; wherein

the cathode terminal has an upper step portion in face-to-face contactwith the cathode member and a lower step portion exposed out of the moldresin portion and

a bottom surface of the mold resin portion and an upper surface of thelower step portion of the cathode terminal are disposed in anapproximately same plane.

According to the above-mentioned configuration, since the mold resindoes not enter in the respective lower surfaces of the anode terminaland the cathode terminal, defects of products due to entering of themold resin can be decreased. Further, since there is no need to protectthe respective lower surfaces of the anode terminal and the cathodeterminal with an insulating tape or the like at the time of molding, theproduction process can be simplified and accordingly, the production ofa solid electrolytic capacitor is made easy and the productionefficiency is improved. Furthermore, since there is no need to adhere aninsulating tape or the like to the respective lower surfaces of theanode terminal and the cathode terminal, it is not required to form aspace between the mold faces of an upper mold and a lower mold inconsideration of the thickness of the insulating tape. Accordingly, theupper mold and the lower mold can be fitted without a gap. As a result,the mold resin can be prevented from leaking out of a boundary betweenthe upper mold and the lower mold.

Further, it is preferable that the cathode terminal further has a risingportion (side portion) upwardly rising from the upper step portion in adirection approximately perpendicular to the direction in which theanode member and the cathode member are aligned and that the risingportion (side portion) is connected with at least one of side surfacesof the capacitor element. According to the above-mentionedconfiguration, since the contact surface area between the cathode memberof the capacitor element and the cathode terminal is increased, the ESRof the solid electrolytic capacitor can be further lowered. The risingportion (side portion) is more preferable to be extended upwardly inboth ends of the upper step portion in the width direction.

Furthermore, it is preferable that the rising portion (side portion)further has an extended portion extending from the anode member sidetoward the cathode member side in the direction in which the anodemember and the cathode member are aligned. According to theabove-mentioned configuration, the contact surface area between thecathode member of the capacitor element and the cathode terminal canfurther be widened and the ESR of the solid electrolytic capacitor canfurther be lowered.

According to one aspect of the present invention, it is made possible toprevent the mold resin from entering in the respective lower surfaces ofthe anode terminal and the cathode terminal. Therefore, defects ofproducts due to entering of the mold resin can be decreased. As aresult, production efficiency can be improved. Further, since there isno need to protect the respective lower surfaces of the anode terminaland the cathode terminal with an insulating tape or the like at the timeof molding, a process of adhering an insulating tape or the like and aprocess of peeling the insulating tape or the like are not needed andthus, it is made possible to simplify the process of production.Accordingly, not only production efficiency can be improved, but alsodeterioration of yield of products can be prevented. Furthermore,according to the present invention, since the upper mold and the lowermold can be fitted without a gap, the mold resin can be prevented fromleaking out of a boundary between the upper mold and the lower mold.Accordingly, defects of products due to leaking the mold resin can bedecreased.

Although the present invention has been described in detail, theforegoing descriptions are merely exemplary at all aspects, and do notlimit the present invention thereto. Various applications ormodifications are possible within the literal or equivalent scope of theclaims.

The present application claims a priority based on Japanese PatentApplication No. 2007-300908 filed on Nov. 20, 2007, the contents ofwhich are hereby incorporated by reference in its entirely.

What is claimed is:
 1. A solid electrolytic capacitor comprising acapacitor element having an anode member and a cathode member, an anodeterminal electrically connected with the anode member, a cathodeterminal electrically connected with the cathode member, and a moldresin portion covering the capacitor element; wherein a lower surface ofthe anode terminal is exposed out of the mold resin portion, the cathodeterminal has an upper step portion and a lower step portion that aredisposed in a direction in which the cathode terminal and the anodeterminal are aligned, an upper surface of the upper step portion isconnected with a lower surface of the cathode member, a lower surface ofthe lower step portion is exposed out of the mold resin portion, atleast a part of an upper surface of the lower step portion is opposed toa part of the lower surface of the cathode member via the mold resinportion, an upper surface of the anode terminal, the upper surface ofthe lower step portion of the cathode terminal, and a bottom surface ofthe mold resin portion between the cathode terminal and the anodeterminal are disposed on an approximately same plane, and the anodeterminal and the cathode terminal have respectively side surfacesexposed out of the mold resin portion and opposed to each other on thebottom surface of the mold resin portion.
 2. The solid electrolyticcapacitor according to claim 1, wherein the cathode terminal further hasa side portion extending from the upper step portion and the sideportion is connected with a side surface of the capacitor element. 3.The solid electrolytic capacitor according to claim 2, wherein the sideportion is upwardly extended from both ends in the width direction ofthe upper step portion to a direction approximately perpendicular to thedirection in which the anode member and the cathode member are aligned.4. The solid electrolytic capacitor according to claim 2, wherein theside portion further has an extended portion extending in a direction inwhich the anode member and the cathode member are aligned.
 5. The solidelectrolytic capacitor according to claim 4, wherein the extendedportion is extended from an anode member side to a cathode member side.6. The solid electrolytic capacitor according to claim 2, wherein theside portion is longer than the upper step portion in the direction inwhich the cathode terminal and the anode terminal are aligned.
 7. Thesolid electrolytic capacitor according to claim 1, wherein the upperstep portion is closer to the anode member than the lower step portionin the direction in which the cathode terminal and the anode terminalare aligned.